As mentioned, select the 'Status/System Logs' drop-down menu item. Click on the firewall tab (Status/System Logs/Firewall). You can then filter the logs via source or destination IP as well as destination port. Type 110 in the destination port field and click on the 'Filter' button. Make sure you've clicked 'dynamic view' so that the logs refresh. Try making a POP3 connection to your mail account and see if the logs show anything being stopped.